Stability relations of manganese oxide minerals in metamorphic orebodies corresponding to sillimanite grade in Gowari Wadhona Mine area, Chhindwara District, Madhya Pradesh, India

Roy, Supriya; Purkait, Pijushkanti

doi:10.2113/gsecongeo.60.3.601

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“…The manganese oxide orebands and the gondites are separate entities, both being regionally metamorphosed products of pure oxidic and oxide-silica sediments, respectively. Such oxidic and oxide-silica sediments have also been transformed by contact metamorphism at Jothvad, Panch Mahals Dt., Gujarat (Champaner=Aravalli Group) and gave rise to oxidic and silicate assemblages, respectively, the latter being termed kodurite because of its composition and contact-metamorphic origin (Roy, 1965(Roy, , 1966(Roy, , 1967.…”

Section: Consequent To the Discussion On The Stability Fields And Trmentioning

confidence: 99%

“…It has been shown earlier (Dorr et al, 1956;Roy, 1965Roy, , 1966) that these metamorphosed silicate-carbonate rocks of manganese were originally laid down in such Eh-pH conditions that deposition of oxides could not take place during sedimentation. Manganese carbonates and sulfides together with manganese silicate and/or free silica were deposited and were later subjected to regional metamorphism.…”

Section: •-Imentioning

confidence: 93%

“…The author (Roy, 1965(Roy, , 1966 has, however, failed to detect any contact-metamorphic rock of the composition of kodurite (spandite-potash felspar-apatite rock) in that area. Krishna Rao (1964) has also concluded later that proper kodurite is absent in Srikakulam Dt.…”

Section: •-Imentioning

confidence: 96%

“…The manganese formations of India, described in Table 5, have been regionally metamorphosed to different grades and have been correlated to corresponding zones of regional metamorphism of pelitic schists (Roy, 1962(Roy, , 1964(Roy, , 1965(Roy, , 1966Roy and Mitra, 1964;Roy and Purkait, 1965). Thus at Shivarajpur, Gujarat, in the chlorite zone, braunire only is developed in the oxidic ores.…”

Section: Mineralogy Of Metamorphosed Manganese Depositsmentioning

confidence: 99%

“…The deposit at Goldongri Hill, Panch Mahals Dt., Gujarat, where the meta-sedimentary manganese formation has been reconstituted by contact metamorphism (pyroxene-hornfels and hornblende-hornfels facies), is also characterized by high-temperature lower-oxide minerals (braunite-hollandite-bixbyitehausmannite in a low-iron bulk composition, interbanded with manganese silicate rocks (kodurite: rhodonite-spandite-blanfordite-brown manganese pyroxene-winchite-alurgite-manganophyllite-apatitequartz; Roy, 1965Roy, , 1966. It is noteworthy that in the extensive sedimentary-metamorphic deposits of India, rhodochrosite or any other manganese-rich carbonate has never been detected.…”

Section: Mineralogy Of Metamorphosed Manganese Depositsmentioning

confidence: 99%

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Mineralogy of the different genetic types of manganese deposits

Roy¹

1968

Economic Geology

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The major manganese deposits of the world can be classified into three broad genetic types: hydrothermal, sedimentary, and superficial. The hydrothermal type includes hypogene vein deposits and those formed in thermal spring aprons. The sedimentary type encompasses both volcanogenic and nonvolcanogenic sediments (ancient continental deposits and recent deep sea nodules) and their metamorphosed equivalents. The superficial type consists of deposits formed by residual concentration, by deposition from meteoric waters and by supergene oxidation-enrichment of pre-existing manganese formations.The mineralogy of all manganese formations belonging to the above genetic types is discussed in detail. It is shown that in deposits formed from hot ascending solutions there is a zonal arrangement of minerals. In the deepest part of the epithermal zone, rhodonite, rhodochrosite, and alabandite, all containing manganese in the Mn " state, are present, followed upwards by hausmannite, bixbyite, braunitc (Mn 2+ and Mn 4+) and ultimately in the uppermost parts, by psilomelane, cryptomelane, pyrolusite, corohaditc, etc. (mainly Mn 4+) in which psilomelane is abundant. In thermal spring aprons also, psilomelane is the most abundant phase. In unmetamorphosed sedimentary deposits the manganese minerals are mainly characterized either by carbonates (rhodochrosite), or higher oxides (pyrolusite, cryptomelane, manganite, psilomelane etc.), the lowtemperature silicates (bementite, neotocite) being rare. The variation in mineralogy of sedimentary bodies can be explained either by the physico-chemical environment of deposition (Eh and pH variation) or by post-depositional diagenetic changes. The metamorphosed sedimentary manganese formations are characterized by varying mineralogy according to the nature of the original sediments and the grade of metamorphism.The oxidic sediments in metamorphosed formations contain the mineral assemblage braunite-bixbyite-hollandite-hausmannite-jacobsite-vredenburgite where some iron and silica are considered to have been present with manganese oxides in original sediments. The carbonate sediments are generally represented by recrystallized rhodochrosite bodies. The mixed sediments of carbonates and silicates are represented by the metamorphic equivalent assemblage of spessartite-rhodonite-rhodochrosite-tephroite and other manganese pyroxenes and amphiboles. The physico-chemical background of the formation of all the above assemblages is discussed. The superficial deposits generally consist of higher oxides of manganese and, depending upon the composition of the original formation and the rate of oxidation, different phases 'appear in the assemblage. The most stable phases are pyrolusite and cryptomelane, but manganite, nsutite and birnessite may also form by restricted oxidation of manganese carbonate formations.

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Section: Consequent To the Discussion On The Stability Fields And Trmentioning

confidence: 99%

Section: •-Imentioning

confidence: 93%

Section: •-Imentioning

confidence: 96%

Section: Mineralogy Of Metamorphosed Manganese Depositsmentioning

confidence: 99%

Section: Mineralogy Of Metamorphosed Manganese Depositsmentioning

confidence: 99%

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